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# Longest Common Prefix Matching | Set-6

• Difficulty Level : Easy
• Last Updated : 12 May, 2021

Given a set of strings, find the longest common prefix.
Examples:

```Input: str[] = {geeksforgeeks, geeks, geek, geezer}
Output: gee

Input: str[] = {apple, ape, april}
Output: ap```

Previous Approaches: Set1 | Set2 | Set3 | Set4 | Set5
Approach:

• Sort the given set of N strings.
• Compare the first and last string in the sorted array of strings.
• The string with prefix characters matching in the first and last string will be the answer.

Below is the implementation of the above approach:

## C++

 `// A C++ Program to find the longest common prefix``#include ``using` `namespace` `std;` `// A Utility Function to find the common prefix between``// first and last strings``string commonPrefixUtil(string str1, string str2)``{``    ``string result;``    ``int` `n1 = str1.length(), n2 = str2.length();` `    ``// Compare str1 and str2``    ``for` `(``int` `i = 0, j = 0; i <= n1 - 1 && j <= n2 - 1; i++, j++) {``        ``if` `(str1[i] != str2[j])``            ``break``;``        ``result.push_back(str1[i]);``    ``}` `    ``return` `(result);``}` `// A Function that returns the longest common prefix``// from the array of strings``void` `commonPrefix(string arr[], ``int` `n)``{``    ``// sorts the N set of strings``    ``sort(arr, arr + n);` `    ``// prints the common prefix of the first and the``    ``// last string of the set of strings``    ``cout << commonPrefixUtil(arr, arr[n - 1]);``}` `// Driver Code``int` `main()``{``    ``string arr[] = { ``"geeksforgeeks"``, ``"geeks"``,``                     ``"geek"``, ``"geezer"` `};``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);` `    ``commonPrefix(arr, n);` `    ``return` `0;``}`

## Java

 `// A Java program to find the longest common prefix` `import` `java.util.Arrays;` `class` `GFG {` `// A Utility Function to find the common prefix between``// first and last strings``    ``static` `String commonPrefixUtil(String str1, String str2) {``        ``String result = ``""``;``        ``int` `n1 = str1.length(), n2 = str2.length();` `        ``// Compare str1 and str2``        ``for` `(``int` `i = ``0``, j = ``0``; i <= n1 - ``1` `&& j <= n2 - ``1``; i++, j++) {``            ``if` `(str1.charAt(i) != str2.charAt(j)) {``                ``break``;``            ``}``            ``result += str1.charAt(i);``        ``}` `        ``return` `(result);``    ``}` `// A Function that returns the longest common prefix``// from the array of strings``    ``static` `void` `commonPrefix(String arr[], ``int` `n) {``        ``// sorts the N set of strings``        ``Arrays.sort(arr);` `        ``// prints the common prefix of the first and the``        ``// last String of the set of strings``        ``System.out.println(commonPrefixUtil(arr[``0``], arr[n - ``1``]));``    ``}` `// Driver Code``    ``public` `static` `void` `main(String[] args) {``        ``String arr[] = {``"geeksforgeeks"``, ``"geeks"``,``            ``"geek"``, ``"geezer"``};``        ``int` `n = arr.length;` `        ``commonPrefix(arr, n);` `    ``}``}``/* This JAVA code is contributed by 29AjayKumar*/`

## Python3

 `# A Python 3 Program to find the``# longest common prefix` `# A Utility Function to find the common``# prefix between first and last strings``def` `commonPrefixUtil(str1, str2):``    ``n1 ``=` `len``(str1)``    ``n2 ``=` `len``(str2)``    ` `    ``result ``=` `""``    ` `    ``# Compare str1 and str2``    ``j ``=` `0``    ``i ``=` `0``    ``while``(i <``=` `n1 ``-` `1` `and` `j <``=` `n2 ``-` `1``):``        ``if` `(str1[i] !``=` `str2[j]):``            ``break``        ``result ``+``=` `(str1[i])``        ` `        ``i ``+``=` `1``        ``j ``+``=` `1` `    ``return` `(result)` `# A Function that returns the longest``# common prefix from the array of strings``def` `commonPrefix(arr, n):``    ` `    ``# sorts the N set of strings``    ``arr.sort(reverse ``=` `False``)` `    ``# prints the common prefix of the first``    ``# and the last string of the set of strings``    ``print``(commonPrefixUtil(arr[``0``], arr[n ``-` `1``]))` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ``arr ``=` `[``"geeksforgeeks"``, ``"geeks"``,``                    ``"geek"``, ``"geezer"``]``    ``n ``=` `len``(arr)` `    ``commonPrefix(arr, n)``    ` `# This code is contributed by``# Sanjit_Prasad`

## C#

 `// C# Program to find the longest``// common prefix``using` `System;` `class` `GFG``{``// A Utility Function to find the common``// prefix between first and last strings``static` `String commonPrefixUtil(String str1,``                               ``String str2)``{``    ``string` `result = ``""``;``    ``int` `n1 = str1.Length, n2 = str2.Length;``    ` `    ``// Compare str1 and str2``    ``for` `(``int` `i = 0, j = 0;``             ``i <= n1 - 1 && j <= n2 - 1; i++, j++)``    ``{``        ``if` `(str1[i] != str2[j])``            ``break``;``        ``result += (str1[i]);``    ``}``    ` `    ``return` `(result);``}` `// A Function that returns the longest``// common prefix from the array of strings``static` `void` `commonPrefix(String []arr, ``int` `n)``{``    ``// sorts the N set of strings``    ``Array.Sort(arr);` `    ``// prints the common prefix of the first``    ``// and the last String of the set of strings``    ``Console.Write(commonPrefixUtil(arr,``                                   ``arr[n - 1]));``}` `// Driver Code``public` `static` `void` `Main()``{``    ``String []arr = {``"geeksforgeeks"``, ``"geeks"``,``                    ``"geek"``, ``"geezer"``};``    ``int` `n = arr.Length;``    ``commonPrefix(arr, n);``}``}` `// This code is contributed by 29AjayKumar`

## PHP

 ``

## Javascript

 ``
Output:

`gee`

Time Complexity: O(N * log N)

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